Well, absolutely not necessary because Sec 22 of KVAT Act, 2003 clearly tells only those dealers who have taxableturnover ( likely to exceed Rs 7.5 lakhs pa or Rs 62.5K pm) are liable to register.

Since Exempted sales do not form part of taxble turnover, you are exempt from registration. But, that does not stop you if you want to opt for Voluntary Registration. Getting a VAT Registration has got other benefits.